1. Field of the Invention
Prelubricating and lubricating systems.
2. Description of the Prior Art
One, although not the only, use of the present invention is in connection with the starting of a stand-by engine which is employed when a main engine fails. A prior art prelubricating system which is quite satisfactory is shown in U.S. L. Pat. No. 3,917,027 granted Nov. 4, 1975. The system of that patent, which was a substantial improvement over prelubricating systems that preceded it as, for example, those shown in U.S. L. Pat. Nos. 3,472,024 granted Oct. 14, 1969, 3,583,525 granted June 8, 1971, 3,583,527 granted June 8, 1971 and 3,722,623 granted Mar. 27, 1973, was predicated upon the use of a stand-by highly pressurized source of hydraulic oil which was employed both to crank a stand-by engine and to energize a prelubricating system, the highly pressurized oil being provided with two work paths, one that cranked the engine and the other that actuated a prelubricating network. The hydraulic resistance of the prelubricating network was lower than the hydraulic resistance of the cranking network, so that when the stand-by engine was called into service the prelubricating network would be rendered operable before the cranking network, thus ensuring prelubricating before starting, i.e. furnishing a very short time delay prior to starting during which time delay the prelubricating was effected.
This system has proven to be an excellent one. It has, however, encountered a certain problem which pertained to engines that used turbochargers. Turbochargers operate at extremely high speeds, a typical speed being 55,000 rpm. A turbocharger does not immediately turn over at a high operational speed. When the engine is cranking there is practically no movement of the turbocharger; but the instant the engine fires, the exhaust gas from the engine is fed to the turbine section of the turbocharger which very quickly comes up to speed, and in from 2 to 3 seconds from the time that the engine has started, by which time the engine is at normal engine running speed, the turbocharger will be rotating at about 50,000 rpm. However, the turbocharger will have reached full speed and will be running for a few seconds, e.g. 4 to 5 seconds, before the lubrication oil from the engine pump reaches the bearings of the turbocharger. This is a "starve" period, although a short one, when damage can occur. It is absolutely essential that the bearings of a spinning turbocharger be continuously oiled to prevent substantial wear or or breakdown of the turbocharger before the engine lubrication pump takes over.
Thus, the system of U.S. L. Pat. No. 3,917,027 was not a suitable one for an engine that had a turbocharger operating in conjunction with it. The prelubricating supplied by this prior patent only would furnish oil to the turbocharger prior to starting of the engine, and there still was a short period of delay in lubricating the turbocharger which began when the prelubricating cycle ended and terminated when the engine was operating at full speed and its oil pump was furnishing oil in a sufficient amount and under a sufficient pressure to the turbocharger. In this short period of about 10 seconds substantial damage could be done to the turbocharger It was desirable that this be eliminated.
Moreover, the prelubricating system of U.S. L. Pat. No. 3,917,027 was restricted in its application of prelubricating oil to existing oil passageways within the engine, since it supplied an initial burst of prelubricating oil to the lubricating system of the engine; that is to say, it supplied prelubricating oil to the sundry passageways and capillaries through which oil delivered by the oil pump of the engine ordinarily would force oil to bearings and the like. It could not, for example, conveniently supply prelubricating oil to the pistons and the cylinders and the valves and sundry relatively movable surfaces throughout the engine in the absence of oil passageways terminating at these various elements and surfaces. Since the cylinders can be dry after long periods of standing, the seal between the piston and cylinder is inefficient, with consequent loss in compression which in a diesel engine will delay firing.
In addition, a similar problem was encountered with starting of engines in general. Thus, it might be desired to start and engine in a very cold climate where oil had congealed or where oil had drained away from relatively movable parts, and it was difficult to force prelubricating oil through passageways filled with viscous oil to these relatively movable parts prior to starting.
Up to the present time no prelubricating or lubricating system has been proposed that would overcome all of these drawbacks.